加热工艺对锌铁合金热成形钢镀层组织的影响

Effect of Heating Process on Coating Microstructure of Galvannealed Hot-formed Steel

利用扫描电镜(SEM)及附带能谱仪系统(EDS),研究了加热工艺对锌铁合金热成形钢镀层组织的影响。结果表明,在传统箱式炉热冲压生产线上,通过适当的方式快冷,使镀层凝固后冲压,可获得表面质量良好、无扩散至基板裂纹的镀层;热冲压后的镀层组织主要由Γ相和α-Fe(Zn)组成,随着加热温度、加热时间的提高,镀层中的Γ相比例下降;为保证基板完全奥氏体化,在890℃的温度下加热180s,镀层中的Γ相比例可达40%,当加热时间提高至360s时,镀层中Γ相消失,将不具备阴极保护作用。

The coating microstructure of galvannealed hot-formed steel after different heating process were studied by scanning electron microscopy(SEM)with energy dispersive spectrometer system(EDS).The results show that the coating after hot stamping with traditional box-type furnace production line have good quality surface and the micro crack can not stretch to the substrate.The coating mainly consisted ofΓphase andα-Fe(Zn),with the heating temperature and heating time increases,the content ofΓphase reduce.In order to keep the substrate fully austenitic,the content ofΓphase can reach to 40%at heating 890℃for 180s.When the heating time increase to 360s,theΓphase disappear and the coating can not offer cathodic corrosion protection.